In conventional waste water treatment systems, there is typically provided, amongst other components, a clarifier or a separator for removing solids from the waste water, and an aeration vessel wherein components of the waste water are oxidized. Because the typical installation employs separators and aeration vessels which are separate from each other, they are relatively costly from the capital standpoint in that excavation costs, the cost of forming the vessels, usually out of concrete, erection costs including painting, plumbing and electrical installations are increased over what would be required if but a single vessel were to be made. Operational expenses are likewise increased in that some means must be provided for returning solids from the bottom of the separator back to the aeration tank which may be costly to operate.
To eliminate these problems, in recent years there have been proposals of oxidation vessels provided with internal separator or clarifier devices. One such construction is illustrated in U.S. Pat. No. 4,303,516 issued Dec. 1, 1981 to Stensel et al. Other proposals wherein clarifiers are included in an aeration basin include the so-called BMTS intrachannel clarifier. It is also believed that a similar design is offered by Aero-Mod, Inc. of Manhatten, Kans.
While such proposals have eliminated or reduced the above enumerated cost factors associated with systems employing separate clarifiers or separators and aeration vessels, they are not without drawbacks of their own. For example, certain of such constructions act as a restriction in the channel of the aeration vessel which effectively acts as a transverse baffle. This in turn blocks movement of scum or floating material requiring the presence of some means for removing the scum and floating material.
The restrictive nature of such systems frequently interferes with the velocity of the waste water moving in the channel such that velocity gradients may occur. Where a low velocity area is generated, undesirable sludge deposition is likely to occur.
Where steps are made to eliminate the velocity problem, the depth of the channel in the vicinity of the clarifier may be made much greater. This in turn increases the construction costs and has the potential problems that may be posed by the existence of significant ground water or, in the alternative, may require expensive excavation in underlying bedrock.
In others, the design of the clarifier may be such as to allow so-called "short circuiting" meaning that the waste water does not flow uniformly through the entire volume of the separator but takes a path of lesser size. This of course means that the velocity of the waste water in the reduced path is increased over the designed velocity which in turn may interfere with the settling of solids in the waste water.
Other prior art of possible relevance includes the following U.S. Pat. Nos.: 3,788,981 issued Jan. 29, 1974 to Richard et al; 3,925,205 issued Dec. 9, 1975 to Sparham; 3,886,064 issued May 27, 1975 to Kosonen; 3,975,276 issued Aug. 17, 1976 to Schmid; and 4,351,733 issued Sept. 28, 1982 to Salzer.
The present invention is intended to overcome the foregoing difficulties.